1/*-
2 *  atrun.c - run jobs queued by at; run with root privileges.
3 *
4 * SPDX-License-Identifier: BSD-2-Clause
5 *
6 *  Copyright (C) 1993, 1994 Thomas Koenig
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. The name of the author(s) may not be used to endorse or promote
14 *    products derived from this software without specific prior written
15 *    permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29/* System Headers */
30
31#include <sys/fcntl.h>
32#include <sys/file.h>
33#include <sys/types.h>
34#include <sys/stat.h>
35#ifdef __FreeBSD__
36#include <sys/sysctl.h>
37#endif
38#include <sys/wait.h>
39#include <sys/param.h>
40#include <ctype.h>
41#include <dirent.h>
42#include <err.h>
43#include <grp.h>
44#include <pwd.h>
45#include <signal.h>
46#include <stdarg.h>
47#include <stddef.h>
48#include <stdio.h>
49#include <stdlib.h>
50#include <string.h>
51#include <syslog.h>
52#include <time.h>
53#include <unistd.h>
54#ifdef __FreeBSD__
55#include <paths.h>
56#else
57#include <getopt.h>
58#endif
59#ifdef LOGIN_CAP
60#include <login_cap.h>
61#endif
62#ifdef PAM
63#include <security/pam_appl.h>
64#include <security/openpam.h>
65#endif
66
67/* Local headers */
68
69#include "gloadavg.h"
70#define MAIN
71#include "privs.h"
72
73/* Macros */
74
75#ifndef ATJOB_DIR
76#define ATJOB_DIR "/usr/spool/atjobs/"
77#endif
78
79#ifndef ATSPOOL_DIR
80#define ATSPOOL_DIR "/usr/spool/atspool/"
81#endif
82
83#ifndef LOADAVG_MX
84#define LOADAVG_MX 1.5
85#endif
86
87/* File scope variables */
88
89static const char * const atrun = "atrun"; /* service name for syslog etc. */
90static int debug = 0;
91
92void perr(const char *fmt, ...);
93void perrx(const char *fmt, ...);
94static void usage(void) __dead2;
95
96/* Local functions */
97static int
98write_string(int fd, const char* a)
99{
100    return write(fd, a, strlen(a));
101}
102
103#undef DEBUG_FORK
104#ifdef DEBUG_FORK
105static pid_t
106myfork(void)
107{
108	pid_t res;
109	res = fork();
110	if (res == 0)
111	    kill(getpid(),SIGSTOP);
112	return res;
113}
114
115#define fork myfork
116#endif
117
118static void
119run_file(const char *filename, uid_t uid, gid_t gid)
120{
121/* Run a file by spawning off a process which redirects I/O,
122 * spawns a subshell, then waits for it to complete and sends
123 * mail to the user.
124 */
125    pid_t pid;
126    int fd_out, fd_in;
127    int queue;
128    char mailbuf[MAXLOGNAME], fmt[64];
129    char *mailname = NULL;
130    FILE *stream;
131    int send_mail = 0;
132    struct stat buf, lbuf;
133    off_t size;
134    struct passwd *pentry;
135    int fflags;
136    long nuid;
137    long ngid;
138#ifdef PAM
139    pam_handle_t *pamh = NULL;
140    int pam_err;
141    struct pam_conv pamc = {
142	.conv = openpam_nullconv,
143	.appdata_ptr = NULL
144    };
145#endif
146
147    PRIV_START
148
149    if (chmod(filename, S_IRUSR) != 0)
150    {
151	perr("cannot change file permissions");
152    }
153
154    PRIV_END
155
156    pid = fork();
157    if (pid == -1)
158	perr("cannot fork");
159
160    else if (pid != 0)
161	return;
162
163    /* Let's see who we mail to.  Hopefully, we can read it from
164     * the command file; if not, send it to the owner, or, failing that,
165     * to root.
166     */
167
168    pentry = getpwuid(uid);
169    if (pentry == NULL)
170	perrx("Userid %lu not found - aborting job %s",
171		(unsigned long) uid, filename);
172
173#ifdef PAM
174    PRIV_START
175
176    pam_err = pam_start(atrun, pentry->pw_name, &pamc, &pamh);
177    if (pam_err != PAM_SUCCESS)
178	perrx("cannot start PAM: %s", pam_strerror(pamh, pam_err));
179
180    pam_err = pam_acct_mgmt(pamh, PAM_SILENT);
181    /* Expired password shouldn't prevent the job from running. */
182    if (pam_err != PAM_SUCCESS && pam_err != PAM_NEW_AUTHTOK_REQD)
183	perrx("Account %s (userid %lu) unavailable for job %s: %s",
184	    pentry->pw_name, (unsigned long)uid,
185	    filename, pam_strerror(pamh, pam_err));
186
187    pam_end(pamh, pam_err);
188
189    PRIV_END
190#endif /* PAM */
191
192    PRIV_START
193
194    stream=fopen(filename, "r");
195
196    PRIV_END
197
198    if (stream == NULL)
199	perr("cannot open input file %s", filename);
200
201    if ((fd_in = dup(fileno(stream))) <0)
202	perr("error duplicating input file descriptor");
203
204    if (fstat(fd_in, &buf) == -1)
205	perr("error in fstat of input file descriptor");
206
207    if (lstat(filename, &lbuf) == -1)
208	perr("error in fstat of input file");
209
210    if (S_ISLNK(lbuf.st_mode))
211	perrx("Symbolic link encountered in job %s - aborting", filename);
212
213    if ((lbuf.st_dev != buf.st_dev) || (lbuf.st_ino != buf.st_ino) ||
214        (lbuf.st_uid != buf.st_uid) || (lbuf.st_gid != buf.st_gid) ||
215        (lbuf.st_size!=buf.st_size))
216	perrx("Somebody changed files from under us for job %s - aborting",
217		filename);
218
219    if (buf.st_nlink > 1)
220	perrx("Somebody is trying to run a linked script for job %s", filename);
221
222    if ((fflags = fcntl(fd_in, F_GETFD)) <0)
223	perr("error in fcntl");
224
225    fcntl(fd_in, F_SETFD, fflags & ~FD_CLOEXEC);
226
227    snprintf(fmt, sizeof(fmt),
228	"#!/bin/sh\n# atrun uid=%%ld gid=%%ld\n# mail %%%ds %%d",
229                          MAXLOGNAME - 1);
230
231    if (fscanf(stream, fmt, &nuid, &ngid, mailbuf, &send_mail) != 4)
232	perrx("File %s is in wrong format - aborting", filename);
233
234    if (mailbuf[0] == '-')
235	perrx("Illegal mail name %s in %s", mailbuf, filename);
236
237    mailname = mailbuf;
238
239    if (nuid != uid)
240	perrx("Job %s - userid %ld does not match file uid %lu",
241		filename, nuid, (unsigned long)uid);
242
243    if (ngid != gid)
244	perrx("Job %s - groupid %ld does not match file gid %lu",
245		filename, ngid, (unsigned long)gid);
246
247    fclose(stream);
248
249    if (chdir(ATSPOOL_DIR) < 0)
250	perr("cannot chdir to %s", ATSPOOL_DIR);
251
252    /* Create a file to hold the output of the job we are about to run.
253     * Write the mail header.
254     */
255    if((fd_out=open(filename,
256		O_WRONLY | O_CREAT | O_EXCL, S_IWUSR | S_IRUSR)) < 0)
257	perr("cannot create output file");
258
259    write_string(fd_out, "Subject: Output from your job ");
260    write_string(fd_out, filename);
261    write_string(fd_out, "\n\n");
262    fstat(fd_out, &buf);
263    size = buf.st_size;
264
265    close(STDIN_FILENO);
266    close(STDOUT_FILENO);
267    close(STDERR_FILENO);
268
269    pid = fork();
270    if (pid < 0)
271	perr("error in fork");
272
273    else if (pid == 0)
274    {
275	char *nul = NULL;
276	char **nenvp = &nul;
277
278	/* Set up things for the child; we want standard input from the input file,
279	 * and standard output and error sent to our output file.
280	 */
281
282	if (lseek(fd_in, (off_t) 0, SEEK_SET) < 0)
283	    perr("error in lseek");
284
285	if (dup(fd_in) != STDIN_FILENO)
286	    perr("error in I/O redirection");
287
288	if (dup(fd_out) != STDOUT_FILENO)
289	    perr("error in I/O redirection");
290
291	if (dup(fd_out) != STDERR_FILENO)
292	    perr("error in I/O redirection");
293
294	close(fd_in);
295	close(fd_out);
296	if (chdir(ATJOB_DIR) < 0)
297	    perr("cannot chdir to %s", ATJOB_DIR);
298
299	queue = *filename;
300
301	PRIV_START
302
303        nice(tolower(queue) - 'a');
304
305#ifdef LOGIN_CAP
306	/*
307	 * For simplicity and safety, set all aspects of the user context
308	 * except for a selected subset:  Don't set priority, which was
309	 * set based on the queue file name according to the tradition.
310	 * Don't bother to set environment, including path vars, either
311	 * because it will be discarded anyway.  Although the job file
312	 * should set umask, preset it here just in case.
313	 */
314	if (setusercontext(NULL, pentry, uid, LOGIN_SETALL &
315		~(LOGIN_SETPRIORITY | LOGIN_SETPATH | LOGIN_SETENV)) != 0)
316	    exit(EXIT_FAILURE);	/* setusercontext() logged the error */
317#else /* LOGIN_CAP */
318	if (initgroups(pentry->pw_name,pentry->pw_gid))
319	    perr("cannot init group access list");
320
321	if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
322	    perr("cannot change group");
323
324	if (setlogin(pentry->pw_name))
325	    perr("cannot set login name");
326
327	if (setuid(uid) < 0 || seteuid(uid) < 0)
328	    perr("cannot set user id");
329#endif /* LOGIN_CAP */
330
331	if (chdir(pentry->pw_dir))
332		chdir("/");
333
334	if(execle("/bin/sh","sh",(char *) NULL, nenvp) != 0)
335	    perr("exec failed for /bin/sh");
336
337	PRIV_END
338    }
339    /* We're the parent.  Let's wait.
340     */
341    close(fd_in);
342    close(fd_out);
343    waitpid(pid, (int *) NULL, 0);
344
345    /* Send mail.  Unlink the output file first, so it is deleted after
346     * the run.
347     */
348    stat(filename, &buf);
349    if (open(filename, O_RDONLY) != STDIN_FILENO)
350        perr("open of jobfile failed");
351
352    unlink(filename);
353    if ((buf.st_size != size) || send_mail)
354    {
355	PRIV_START
356
357#ifdef LOGIN_CAP
358	/*
359	 * This time set full context to run the mailer.
360	 */
361	if (setusercontext(NULL, pentry, uid, LOGIN_SETALL) != 0)
362	    exit(EXIT_FAILURE);	/* setusercontext() logged the error */
363#else /* LOGIN_CAP */
364	if (initgroups(pentry->pw_name,pentry->pw_gid))
365	    perr("cannot init group access list");
366
367	if (setgid(gid) < 0 || setegid(pentry->pw_gid) < 0)
368	    perr("cannot change group");
369
370	if (setlogin(pentry->pw_name))
371	    perr("cannot set login name");
372
373	if (setuid(uid) < 0 || seteuid(uid) < 0)
374	    perr("cannot set user id");
375#endif /* LOGIN_CAP */
376
377	if (chdir(pentry->pw_dir))
378		chdir("/");
379
380#ifdef __FreeBSD__
381	execl(_PATH_SENDMAIL, "sendmail", "-F", "Atrun Service",
382			"-odi", "-oem",
383			mailname, (char *) NULL);
384#else
385        execl(MAIL_CMD, MAIL_CMD, mailname, (char *) NULL);
386#endif
387	    perr("exec failed for mail command");
388
389	PRIV_END
390    }
391    exit(EXIT_SUCCESS);
392}
393
394/* Global functions */
395
396/* Needed in gloadavg.c */
397void
398perr(const char *fmt, ...)
399{
400    const char * const fmtadd = ": %m";
401    char nfmt[strlen(fmt) + strlen(fmtadd) + 1];
402    va_list ap;
403
404    va_start(ap, fmt);
405    if (debug)
406    {
407	vwarn(fmt, ap);
408    }
409    else
410    {
411	snprintf(nfmt, sizeof(nfmt), "%s%s", fmt, fmtadd);
412	vsyslog(LOG_ERR, nfmt, ap);
413    }
414    va_end(ap);
415
416    exit(EXIT_FAILURE);
417}
418
419void
420perrx(const char *fmt, ...)
421{
422    va_list ap;
423
424    va_start(ap, fmt);
425    if (debug)
426	vwarnx(fmt, ap);
427    else
428	vsyslog(LOG_ERR, fmt, ap);
429    va_end(ap);
430
431    exit(EXIT_FAILURE);
432}
433
434int
435main(int argc, char *argv[])
436{
437/* Browse through  ATJOB_DIR, checking all the jobfiles wether they should
438 * be executed and or deleted. The queue is coded into the first byte of
439 * the job filename, the date (in minutes since Eon) as a hex number in the
440 * following eight bytes, followed by a dot and a serial number.  A file
441 * which has not been executed yet is denoted by its execute - bit set.
442 * For those files which are to be executed, run_file() is called, which forks
443 * off a child which takes care of I/O redirection, forks off another child
444 * for execution and yet another one, optionally, for sending mail.
445 * Files which already have run are removed during the next invocation.
446 */
447    DIR *spool;
448    struct dirent *dirent;
449    struct stat buf;
450    unsigned long ctm;
451    unsigned long jobno;
452    char queue;
453    time_t now, run_time;
454    char batch_name[] = "Z2345678901234";
455    uid_t batch_uid;
456    gid_t batch_gid;
457    int c;
458    int run_batch;
459#ifdef __FreeBSD__
460    size_t ncpusz;
461    double load_avg = -1;
462    int ncpu;
463#else
464    double load_avg = LOADAVG_MX;
465#endif
466
467/* We don't need root privileges all the time; running under uid and gid daemon
468 * is fine.
469 */
470
471    RELINQUISH_PRIVS_ROOT(DAEMON_UID, DAEMON_GID)
472
473    openlog(atrun, LOG_PID, LOG_CRON);
474
475    opterr = 0;
476    while((c=getopt(argc, argv, "dl:"))!= -1)
477    {
478	switch (c)
479	{
480	case 'l':
481	    if (sscanf(optarg, "%lf", &load_avg) != 1)
482		perr("garbled option -l");
483#ifndef __FreeBSD__
484	    if (load_avg <= 0.)
485		load_avg = LOADAVG_MX;
486#endif
487	    break;
488
489	case 'd':
490	    debug ++;
491	    break;
492
493	case '?':
494	default:
495	    usage();
496	}
497    }
498
499    if (chdir(ATJOB_DIR) != 0)
500	perr("cannot change to %s", ATJOB_DIR);
501
502#ifdef __FreeBSD__
503    if (load_avg <= 0.) {
504	ncpusz = sizeof(size_t);
505	if (sysctlbyname("hw.ncpu", &ncpu, &ncpusz, NULL, 0) < 0)
506		ncpu = 1;
507	load_avg = LOADAVG_MX * ncpu;
508    }
509#endif
510
511    /* Main loop. Open spool directory for reading and look over all the
512     * files in there. If the filename indicates that the job should be run
513     * and the x bit is set, fork off a child which sets its user and group
514     * id to that of the files and exec a /bin/sh which executes the shell
515     * script. Unlink older files if they should no longer be run.  For
516     * deletion, their r bit has to be turned on.
517     *
518     * Also, pick the oldest batch job to run, at most one per invocation of
519     * atrun.
520     */
521    if ((spool = opendir(".")) == NULL)
522	perr("cannot read %s", ATJOB_DIR);
523
524    if (flock(dirfd(spool), LOCK_EX) == -1)
525	perr("cannot lock %s", ATJOB_DIR);
526
527    now = time(NULL);
528    run_batch = 0;
529    batch_uid = (uid_t) -1;
530    batch_gid = (gid_t) -1;
531
532    while ((dirent = readdir(spool)) != NULL) {
533	if (stat(dirent->d_name,&buf) != 0)
534	    perr("cannot stat in %s", ATJOB_DIR);
535
536	/* We don't want directories
537	 */
538	if (!S_ISREG(buf.st_mode))
539	    continue;
540
541	if (sscanf(dirent->d_name,"%c%5lx%8lx",&queue,&jobno,&ctm) != 3)
542	    continue;
543
544	run_time = (time_t) ctm*60;
545
546	if ((S_IXUSR & buf.st_mode) && (run_time <=now)) {
547	    if (isupper(queue) && (strcmp(batch_name,dirent->d_name) > 0)) {
548		run_batch = 1;
549		strlcpy(batch_name, dirent->d_name, sizeof(batch_name));
550		batch_uid = buf.st_uid;
551		batch_gid = buf.st_gid;
552	    }
553
554	/* The file is executable and old enough
555	 */
556	    if (islower(queue))
557		run_file(dirent->d_name, buf.st_uid, buf.st_gid);
558	}
559	/*  Delete older files
560	 */
561	if ((run_time < now) && !(S_IXUSR & buf.st_mode) && (S_IRUSR & buf.st_mode))
562	    unlink(dirent->d_name);
563    }
564    /* run the single batch file, if any
565    */
566    if (run_batch && (gloadavg() < load_avg))
567	run_file(batch_name, batch_uid, batch_gid);
568
569    if (flock(dirfd(spool), LOCK_UN) == -1)
570	perr("cannot unlock %s", ATJOB_DIR);
571
572    if (closedir(spool) == -1)
573	perr("cannot closedir %s", ATJOB_DIR);
574
575    closelog();
576    exit(EXIT_SUCCESS);
577}
578
579static void
580usage(void)
581{
582    if (debug)
583	fprintf(stderr, "usage: atrun [-l load_avg] [-d]\n");
584    else
585	syslog(LOG_ERR, "usage: atrun [-l load_avg] [-d]");
586
587    exit(EXIT_FAILURE);
588}
589